Re: [Qemu-devel] [RFC][PATCH 28/45] qemu-kvm: msix: Drop tracking of used vectors

[Jan Kiszka]

On 2011-10-21 09:54, Michael S. Tsirkin wrote:
> On Fri, Oct 21, 2011 at 09:09:10AM +0200, Jan Kiszka wrote:
>> On 2011-10-21 00:02, Michael S. Tsirkin wrote:
>>>>> Yes. But this still makes an API for acquiring per-vector resources a 
>>>>> requirement.
>>>>
>>>> Yes, but a different one than current use/unuse.
>>>
>>> What's wrong with use/unuse as an API? It's already in place
>>> and virtio calls it.
>>
>> Not for that purpose.
>> It remains a useless API in the absence of KVM's
>> requirements.
>>
> 
> Sorry, I don't understand. This can acquire whatever resources
> necessary. It does not seem to make sense to rip it out
> only to add a different one back in.
> 
>>>
>>>> And it will be an
>>>> optional one, only for those devices that need to establish irq/eventfd
>>>> channels.
>>>>
>>>> Jan
>>>
>>> Not sure this should be up to the device.
>>
>> The device provides the fd. At least it acquires and associates it.
>>
>> Jan
> 
> It would surely be beneficial to be able to have a uniform
> API so that devices don't need to be recoded to be moved
> in this way.

The point is that the current API is useless for devices that do not
have to declare any vector to the core. By forcing them to call into
that API, we solve no current problem automatically. We rather need
associate_vector_with_x (and the reverse). And that only for device that
have different backends than user space models.

Jan

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